From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 399412FC865 for ; Wed, 29 Oct 2025 10:26:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761733608; cv=none; b=SqCRFZKHNbZ3nZSErF/mrysIZt5Ff2MDA6+lxKvcNrRYtVOhA4c2HZx/aSHLA0933mMuCVXMsanJUUGF1+iwL/moXQ6YDJ4X3G4LzADWEiwAPNv9++vtQHMOqrppSYJR8vfVVmuQtcCYxN358yal+5bEmS00aeorESg3nFgpOJU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761733608; c=relaxed/simple; bh=zkE0vyis83Qnd4j3qFtBbD4uxT5fDgXxEKk32YXAR1I=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=KMP52+mkiVeYZ10804GuwZgaspPxZCWeOoljaSShoF2S8OHQoJy8r7alHB1TmD2ITzFkj37PdacvwfHQobtRQwHIgXPJWddVa3mg7vHO90L5P+Zci794MtGWVVx3BqiLTixxKtj1n3Ma6wHmYIZgPIkheKck91SwBBgGRg3xIQ0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=cnncW+AO; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="cnncW+AO" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1761733606; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=/l/eBTg6PDk2gq24yxrQmlGvSlksP+1NRV8KnJwBP8E=; b=cnncW+AON+djwLkCGRV01SWIpFPM/uefZqgxtKSyfKIdwhdN2cEMX5WYCgx9cWmbY//jV0 aPxQfs0D+r5sOG5glob+B5YMFQLOI6VfJZw/5nsCWh3cW2TILgfBEDWjLQrBC3S0cq1RoZ 2mDCh4qfsQy9PIfuMEbjTEw8m8Mq/hE= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-547-QVJke5ANNZ2g6Brlfu5tgQ-1; Wed, 29 Oct 2025 06:26:45 -0400 X-MC-Unique: QVJke5ANNZ2g6Brlfu5tgQ-1 X-Mimecast-MFC-AGG-ID: QVJke5ANNZ2g6Brlfu5tgQ_1761733604 Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-47106720618so50907825e9.1 for ; Wed, 29 Oct 2025 03:26:44 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1761733604; x=1762338404; h=content-transfer-encoding:in-reply-to:autocrypt:content-language :from:references:cc:to:subject:user-agent:mime-version:date :message-id:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=/l/eBTg6PDk2gq24yxrQmlGvSlksP+1NRV8KnJwBP8E=; b=m6zWlWkWCwK1TjMJ0/sOOGlKcXarX2jTft4+2Ban0X15ZBLTxAntYNsWGWgAGcLZbd IiPg6Srv77Qoyto1iVCVcKTA4DWDhJCjv23CSmSho21EWl0IIXmR2DKGd84zbVd4XsZy MsKwI+Tj7hCwHtFu/1Rbr0UQnmBDtER2iveLBhop0EzrpWBMPvjKyzqBZXGwypTBYj4x EeJF/g47WWJ+y8BumZQsNMeAhTj5FDnenEq4OJIF8xfU3vrEqE4mCF7/H1bUYK/N2aQS tC960N+nTqy6S2z7GTxNhJTfEudnl7RCkT6svIJMt2klLgjQjo1kyxxro1r4k3u5NDRi gb1g== X-Forwarded-Encrypted: i=1; AJvYcCUoUsmvhPBnOstNh+/7lIQ+YG6Wa+CMzhfwKK1AGgANLrDkQNLovIylDk5/fEKMrkXwNs/bgsmoW0vdb8w=@vger.kernel.org X-Gm-Message-State: AOJu0YxwcDAudhQVagzlMr2u3f4NsnxYvrd16M4/bo0x+1t5axguEand p5vG30v7Rc89VyIx3+rgcvm4dmZVnfK9NNPb9gZ6TuChSLurkrwj0x7peEfhD5KHqUkGeZvdw5O 7lM+JLcOE5ZehKLpRIdgLldMk+iRLbVTDk4OzS0P3/ooWMxkysi6XAp3YRmkl774ALg== X-Gm-Gg: ASbGncuPc6Gzx4X+Jt2H13++dl2IKGnzBCD+BXWByRnCk+sM0OXFlHoTFNtTzczu9v0 B7041Seowy6MkzNEIUpSKaDrFD/pj1PkY6liFT4PDa5DVsPTCx0i+gCVzg2TOyGkXYJE5ACpY44 NqF3ovon+fA//J+8BMY+t1SYtYHS0vK8X9Z8ThdYSlzbUgY/bwG7q8XtAvHFLpjg9ANs3rU5XW5 bN3gdmOahlyM1GuGwJXXz+HwwmGmhBUNlitRMfTXKhckUViYN7osR49GtOgzmb3FqfIygLasoGj QmdEI6D70/dh4di27uLDA+VOHweY+nqtFQelwpfaliYG+DzRB6R2B1abaKPHAlsRy/2Cisj4+oZ ih5fhXv9c/mXAqW0yer7evQ== X-Received: by 2002:a05:600c:4591:b0:471:115e:624b with SMTP id 5b1f17b1804b1-4771e18cc1fmr23359195e9.17.1761733603675; Wed, 29 Oct 2025 03:26:43 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGtQTrCoapOr6bX5uVmtmRqcuUC4lYBRzIXvtaTPDducTLRlHN+f7pxZPgextJafstOMsxSuw== X-Received: by 2002:a05:600c:4591:b0:471:115e:624b with SMTP id 5b1f17b1804b1-4771e18cc1fmr23358735e9.17.1761733603198; Wed, 29 Oct 2025 03:26:43 -0700 (PDT) Received: from [10.32.64.156] (nat-pool-muc-t.redhat.com. [149.14.88.26]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4771e202093sm43202745e9.11.2025.10.29.03.26.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 29 Oct 2025 03:26:41 -0700 (PDT) Message-ID: Date: Wed, 29 Oct 2025 11:26:39 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/3] Optimize code generation during context To: Xie Yuanbin , riel@surriel.com, linux@armlinux.org.uk, mathieu.desnoyers@efficios.com, paulmck@kernel.org, pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, davem@davemloft.net, andreas@gaisler.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, luto@kernel.org, peterz@infradead.org, acme@kernel.org, namhyung@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, anna-maria@linutronix.de, frederic@kernel.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, thuth@redhat.com, akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, segher@kernel.crashing.org, ryan.roberts@arm.com, max.kellermann@ionos.com, urezki@gmail.com, nysal@linux.ibm.com Cc: x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linux-perf-users@vger.kernel.org, will@kernel.org References: <18734a4944e47952b7ad3e10a36c902392bdaa91.camel@surriel.com> <20251025173700.754-1-qq570070308@gmail.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20251025173700.754-1-qq570070308@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 25.10.25 19:37, Xie Yuanbin wrote: > On Fri, 24 Oct 2025 17:36:06 -0400, Rik van Riel wrote: >> Also, what kind of performance improvement >> have you measured with these changes? > > When I debugged performance issues before, I used the company's equipment. > I could only observe the macro business performance data, but not the > specific scheduling time. Today I did some testing using my devices, > and the testing logic is as follows: > ``` > - return finish_task_switch(prev); > + start_time = rdtsc(); > + barrier(); > + rq = finish_task_switch(prev); > + barrier(); > + end_time = rdtsc; > + return rq; > ``` > > The test data is as follows: > 1. mitigations Off, without patches: 13.5 - 13.7 > 2. mitigations Off, with patches: 13.5 - 13.7 > 3. mitigations On, without patches: 23.3 - 23.6 > 4. mitigations On, with patches: 16.6 - 16.8 Such numbers absolutely have to be part of the relevant patches / cover letter to show that the compiler is not actually smart enough to make a good decision. Having that said, sometimes it helps to understand "why" the compiler does a bad job, and try to tackle that instead. For example, compilers will not inline functions that might be too big (there is a compiler tunable), factoring out slow-paths etc could help to convince the compiler to do the right thing. Of course, it's not always possible, and sometimes we just now that we always want to inline. -- Cheers David / dhildenb